1. Field of the Invention
This invention concerns clutch controlled automotive type fan drive devices, and more particularly, electromagnetically operated temperature controlled clutching of the drive to the engine cooling fan.
2. Description of the Prior Art
Automotive cooling fans consume significant power, particularly at higher engine speeds where the augmentation of air flow by the fan is not usually necessary for adequate engine cooling. Thus, it has heretofore been recognized that it would be advantageous to provide a fan drive which would disconnect the drive at higher engine speeds, or whenever the engine was being adequately cooled as evidenced by a thermal sensor. Noise levels would also be reduced.
However, the additional expense of these drives has not been offset by the fuel savings until the recent great increases in fuel prices. This situtation has created a market for retrofitting such drives particularly for truck applications in which the economics of operation are critical.
Prior art fan devices of this type have suffered from various design deficiencies; particularly in such retrofit applications.
The addition of this fan drive has increased the axial length of the assembly, creating the need for relocation of shrouding, etc., and rendering the device relatively bulky. Installation of the unit may also necessitate an axial clearance for attachment bolts.
In electromagnetic designs, an inner body element is often included which is configured with arcuate slots joined with relatively thin web sections to provide a proper magnetic flux path, and in many designs this element has supported fan or pulley loads, increasing the incidence of failure of this element.
It is an object of the present invention to provide such a controlled operation automotive cooling fan drive which is particularly suited to such retrofit applications and which does not incorporate such design deficiencies as described.
It is a further object to provide such a fan drive which has certain additional advantages as will be described.